Identifying Barriers to Solar and Storage Hybrids: Modeled vs. empirical wholesale market value and net-value for co-located solar + storage projects

Large-scale (1MW+) co-located solar and battery storage projects are expanding rapidly in the United States, but their realized contribution to the bulk power system remains poorly understood because public project-level operating data are limited. The Lawrence Berkeley National Laboratory estimates the wholesale market value of 280 operational photovoltaic-plus-storage (PV+S) projects across the seven ISOs/RTOs and 19 additional balancing authorities, representing roughly 95% of the U.S. PV+S fleet in 2024. We model optimized hourly dispatch under energy, capacity, and ancillary-service market opportunities and compare the resulting value with standalone PV value, project-specific levelized cost estimates, and empirical operating or revenue data where available.

According to optimized dispatch with perfect price foresight, adding batteries could have increased the national generation-weighted market value of solar from $29/MWh to $75/MWh in 2024, primarily through higher capacity value, followed by ancillary-service and energy shifting revenue. For projects with available cost data, optimized PV+S market value exceeded levelized generation cost by nearly $35/MWh from 2020–2024 when accounting for tax credits. Empirical operations of 51 projects captured substantial but incomplete value: in 2024, observed PV+S operations realized $39/MWh, or 62% of modeled optimized value, with the storage premium reaching only 38% of its optimized potential.

The gap between optimized and empirical value reflects multiple barriers that prevent projects from offering their full value to the bulk power system, including: limited participation in wholesale markets such as ancillary services that remain lucrative in some regions; tax-driven grid-charging restrictions for older projects; simplistic rule-based dispatch (charge in the middle of the day and discharge in the evening); imperfect price and generation forecasting; weak or missing price signals in non-ISO regions; and dispatch incentives tied to contracts or state programs rather than bulk-system value. These findings suggest that PV+S can be cost-effective from a wholesale-market perspective, but that improved market participation, forecasting, and alignment of operational incentives are needed for projects to realize their full system value proposition. 

The research is made available in several formats, including:

• A Briefing slide deck
• A public data file with annual (2020-2024) market value estimates of PV and PV+S projects from the optimized base scenario.
• Plant-level hourly modeled PV generation + storage dispatch estimates can be downloaded at the Open Energy Data Initiative (OEDI) at https://data.openei.org/submissions/8687.